My first visit to the Half Shell came during a gas outage that left them unable to cook anything. The bartender's recommendation of the Ahi Tuna Caesar was excellent and uncooked of course.
My second visit (with Mom) was to satisfy a need for a quick meal and at a near-by location. While these are not always the best circumstances to visit any establishment, I am always psyched when it turns out to be a good experience.
We ordered the happy hour seafood nachos. Not only was the price perfectly appropriate, but the nachos were exceptionally tasty and in a portion that proved to be too much for the two of us to finish.
To be fair, I could not remember the server at all, which is not itself a bad thing. Sometimes the food needs to be raised up on a pedestal so it can be fairly evaluated without the distraction of bad (or good) service.
I have no doubt that my two visits here would have inspired a 5 star rating had the service been great each time (because the food has been), but as-it-stands, the service was just okay, thus the four stars.